System of motor control.



L. PLEISCHMANN.

SYSTEM OF MOTOR CONTROL.

APPLICATION FILED MAY 3,1912v Patented July 7, 1914.

1715 A TITURNEY.

,larly to a system of speed control 0 UNITED STATES PATENT orrioa.

LIONEL FLEISCHMANN, 0F BERLIN, GERMANY, ASSIGNOR TO GENERAL ELECT'EZG COMPANY,'A CORPORATION OF NEW YORK.

SYSTEM or MOTOR CONTROL.

To all whom it may concern Be it known that I, LIONEL FLmsoHMANN, a-citizen of the'United' States, residing at Berlin, Germany, have invented certain new and useful Improvements in Systems of Motor Control, of which the following is a specification. I ,2 v My invention relates to a system of control of electric motors and more induction motors in which the energytaken from the secondary thereof is transformed .by means of a rotary transformer into direct current electrical energy or'v into electrical energy of a differentfrequency and is utilized in any Well known manner. "In such motor control systems, it is often desirable to "vary the speed of the induction motor, and consequently the slip of the motor over a Wide range. In order to vary the speed of the induction motor it has heretofore been necessary to construct the rotary transformer so that it. is capable of a great range of regulation, because the rotary transformer has been connected directly to the secondary of the induction. motor and consequently its speed varies with the frequency of the slip currents of the induction motor.

My invention has for its object to provide such a system of control for an induction motor in which the rotary transformer maybe of simple construction and need not be capable of such a great range of regulation.

To this end, one feature of my invention consists in providing. in such a system of induction motor control, a dynamo electric machine connected in cascade between the rotary tIHHSfOIll'ltl and the induction motor,.the speed ofwhich is to vbe controlled.

Another feature of my invention consists in utilizing the dynamo electric machine as an alternating current booster when it no longer forms a part-of the system of speed control of the induction motor. Preferably the dynamo electric machine is connected in cascade between the rotary transformer and the induction motor for operation of the induction motor at a slow speed and as an alternating current booster between the induction motor and the rotary transformer for operation of the induction motor at a higher speed. Throughout the specification and claims l mean by a rotary trans- Specification of Letters Patent.

Application filed May-3, 1912.

particu- Patepted July 7, 19%;. Serial No. 694,830,

former, a dynamo electric machine or motorgenerator set which transforms electrical energy from one frequency to another or to direct current:

Other features of novelty which characterize my invention will be pointed out with particularity/in the claims annexed to and forming apart of this specification.

My invention will best be understood reference to the following description taken in connection with the accompanyin9, drawing. in which the single figure shows diagrammatically a systcn'i arranged in accordance with my invention. Referring to the drawing, A

duction motor, the speed of wh to he controlled and which is supplied with alternating current from an alternating current source, as the lines ll. B is a rotary trans former of any uitable type for t tyllisftillib inc; alter-nulls current electrical energy from one frc nwncy to another, or to direct current. in the particular system which i have chosen to illustrate, l have shown the rotary transformer as a rotary converter. Energy taken from the secondary of the induction motor A is transformed by the rotary.transformer B and is utilized in any well known manner.

(7 is a dynamo electric machine which is preferably mechanically connected to the rotary transformer B. The dynamo electric machine 0 is connected incascade as a frequency changer between the rotary transformer B and the induction motor Aby me of a-switch D when the indaction motor 1 is operating at one speed, preterahly a low speed, or, in other words, at a. high slip, in. which case the frequency and the voltage of the rotor or secondary currents of the induction motor A are ci'imparatii'ely high, and the rotary transformer B is connected as a simple rotary transformer by the switch D when the motor is operating at a diil'eo ent speed. preferably a higher speed. in which case the frequency and voltage of the rotor currents thereof are smaller. 4 preferred form of my ini'enti z'i. I the dynamo electric machine C as an ai. Y nating, current booste for the rotary trans former when the motor A is operating at a high speed. in order to operate the dynamo electric in: chine (in as an alternating current bo stcr. l supply its rotor or stator wi direct current from a suitable source.

s an inhave chosen to show this source of direct current as a storage battery E, which may be, however, any suitable source of direct curre Inhe drawings I have shown my invention applied to the particular system of the British Patent No. 25,147 of 1905,; in which an auxiliary dynamo electric machine F, which is preferably a direct current machine, is mechanically connected to the rotor of the induction motor A and is supplied.

the switch D is in the position shown in the drawing, n aking contact with contacts 1, 3, 5, 6, 8 and 10, in which case the energy flowing out of the secondary of the motor A is taken into the stator of the dynamo electric machine C which is. connected in Y,

since the contacts (-3, 8 and 10, engaged by the switch D, are short-circuited. The rotor windings of the machine 0 are connected to the rotary transformer B. Since the windings of the machine C are connected as just explained, this machineis connected in cascade between the rotarj transformer B and the induction motor A. The rotary'transformer B transforms the energy from the Why a field winding? secondar of the machine G into direct current, which is then supplied to the direct current machine F. The rotary transformer B is shown as being excited by a field winding 1) which is supplied with constant excitation from the battery E and the direct current machine F .is shown as being excited connected to the storage battery E in series with a rheostat R. The speed of the induction motor A may be var1ed by varying the excitation of the field winding In order to change the speed of the motor A, the field of the motor F is changed. For example, by increasing the amount of resistan e inseries with the field winding f-, the motor F will thus tend to increase the speed of the induction motor A, because by weakening the field of the motor F, it will take more current. from the rotary transformer B so that the secondary of the induction motor A will supply more current to the rotary converter through the dynamo electric machine C, and consequently the mam-om motor A. will develop a greater torque which will tend to increase its speed. The motor F will also tend to increase the speed of the induction motor because its c umtcr-elcctromotive force is re, duced, because of its weakened field. It will therefore be seen that by adjusting the rheostat R, any required speed of the induction motor can be obtained. The electrical energy converted in the rotor of the induction motor A is utilized by passing it through the'machine C, the rotary converter B an the direct current n'achine F, and .is returned to the source through the shaft of the motor A in the form of mechanical energy. If, therefore, the energy outputof the direct current clrcuit be kept constant, the output of the induction motor will also be kept constant. Since with the switch D in the position described above, the dynamo electric machine C is connected in cascade between the rotary transformer B and the induction motor A, the machines B and O operate at a speed which is equal to twice the frequency of the secondary current of the induction motor A divided by the sumof the number of their poles. If new the speed of the induction motor A has been increased so that the frequency of the secy ondary currents is small, the switch D is operated to make contacuwith'contacts 2,. 4, 7, '9 and 11. When the switch is in this position, the dynamo electric machine 0 no longer forms a part of the system of speed control of the induction motor A, but I prefer to use it as an alternating current. booster in series with' the rotary trans former B. As will be seen from the drawing, the stator windings are connectedyin series between the collector rings of the rotary transformer B and the collector rings of the induction motor A. The source of direct current E is connected 'to two of the collector rings of the rotor winding of dynamo electric machine C and-supplies direct 10c current to the rotor winding. By suitably choosing the voltage of the excitation supplied to the rotor of the dynamo electric machine C, or by regulating it, the voltage supplied to the rotary transformer B and,

therefore, the direetcurrent voltage supplied to the motor F may be made such, that the armature voltage of the machine F with the" same range of regulation of the speed of the motor A, varies within small 1 lin-its, whereby the machine F may be made smaller. lVith the switch in this position,

the rotary transformer B is connected as-a simple rotary transformer and will operate at a speed equal to -twice the frequency of the secondary current of the induction mo-.,

for A divided by the number of poles of the transformer B.

When the dynamo electric machine C is connected in cascade between the rotary transformer B and the-induction motor A, t-h 9 with the slip of the induction motor A (11- speed of therotary transformcuvari'cs vided by the sum of the number of poles of I the machines 13 and C, and when connected as a simple rotary transformer its speed varies with thelslip divided only by the number of polesof the machine ii; it, will therefore be seen that it is possible, by connecting the dynamo electric machine C- M 3 a simple between the rotary transformer B motor A or by connecting the rotary the speed of the induction motor great range while the speed of the rotary transformer varied over a much sma range. For example. when. the in- '11 motor is operating with a iargo slip connected in cascade l cthe rotary l. ansformer and the motor 7 1 consequently the rotary transformer iassuming the number of its poles equals the nor er of poles on the machine G) is operating at a speed of only one-half of what it would he operating if it were connected rotary transformer, and when the induction motor is operating with a small slip, the rotary transformer B is connect-cd as a simple rotary transformer. -[f dcsired, the field of the machine F may be regulated automatically, as for example, as described in the British atcnt No. 25,147 of 1995.

I desire it to be understood that my in vcntion. is not limited to the particular system shown and described, and I aim in the appended claims to cover all modifications which. do not depart from the spirit and s ope of my in yeniion.

What I claim new and desire to secure by 'iletteis Patent of the United States, is

i. In a system of otor control, an induction motor, and means for regulating the speed of said induction motor by utilizing energy. taken from the sccOndary of the induction motor comprising a rotary transformer. .2 dynamo electric machine, and nzcaus for connecting said dynamo electric machine in cascade between said rotary transformer and said induction motor for operation of said induction motor at one sgioed a for connecting said rotary transa simple rotary transformer for aiion of said induction motor at a difirent speed.

52. in a ,1 stcm of motor controi. an inducti n .il i'li't'll, and means for regulating the pec-ii of said induction motor by utilizing inn taken from tho S9C0litl4lj of the in duction motor comprising a rotary transf .r, a dynamo electric machine, and for connecting said dynamo electric machine in cascade between said rotary tral:sf ru'icr and said. induction. motor for "1; cpel'aiion of said induction motor at a low sp nd and for connecting said rotary trnusfornum as a simple rotary transformer for operation of said induction motor at a high speed.

3. in a. svatcm of motor control, an induc- (ion motor. and means for regulating the speed of said induction motor by utilizing energy taken from the secoiulary of said induction motor comprising a rotary transformer, dynamo electric machine, and

mcr a simple rotary transformer,

former, a dynamo electric machine, and

means for connecting said dynamo electric machine in cascade between said induction motor and said rotary transformer for 01)- cration of said induction motor at a low speed and for connecting said dynamo electric machine as an alternating current booster in series with said rotary transformer for operation of said induction m0- tor at a high speed.

5. In a system of motor cont1'ol,.an induction motor, means for regulating the speed I of said induction motor by utilizing energy taken from the secondary of the induction motor comprising a rotary transformer for transforming alternating current into direct current, a direct current machine mechanically connected to said induction motor and supplied with current from said rotary transformer, a dynamo electric machine, and means for connecting said dynamo electric machine in cascade between said rotary transformer and said induction motor for operation. of said induction-motor at one speed and for connecting said rotary transformer as a simple rotary transformer for operation of said i1 luction motor at a different speed.

6. In a system of motor control, an induction motor. means for regulating the speed of said induction motor by utilizing energy taken from the secondary of the induction motor con'iprising a rotary transformer for transforming alternating current into direct current, a direct current machine mechanically connected to said induction motor and supplied with current from said rotary transformer. a dynamo electric machine, and means for connecting mid dynamo electric machine in cascade octween said rotary transformer and said induction motor for operation of said induction motor at a low spec-d and for cnnuwling said rotary transformer as a simple rotary transformer for operation of said induction motor at a high speed.

7. In a system of motor control, an induction motor. means for regulating the speed of said induction motor by'utilizing pncrgy taken from the secondary of the piduction motor com rising a rotary trausormcr for transforming alternating current into direct current, a direct current ma chine mechanically connected to saidinduc lion motor and supp ied with current from said rotary transformer, a dynamo electric machine. and means for connecting said dynamo electric machine in cascade as a frequency changer or as an alternating current booster between said rotary transformer and said induction motor.

8. In a system of motor controhan induction motor, means for regulating the speed of said induction motor by utilizing energy taken from the secondary of the induction motor comprising a rotary transformer for transforming alternating current into direct current, a direct current machine mechanically connected to said induction motor and supplied with current from said rotary transformer, a dynamo electric machine, and means for connecting said dynamo electric machine in cascade as a frequency changer between said induction motor and said rotary transformer" for op eration of said inducti n motor at a slow speed and for connecting said dynamo electric machine as an alternating current booster in series with said rotary transformer for'operation of said induction motor at a high speed.

9. In a system of motor control, an induction motor, means for regulatio the speedot said induction motor by utilizing energy taken from the secondary of the indnction motor comprising a rotary trans former, a dynamo (lPCiIIlC machine having a stator winding and a rotor winding provided with collector rings, a source of direct cur ent, and means for connecting said dynamo electric r achine in cascade between said mtarytrm irmer and said induction motor for peration of said indu tion Inotnr at one speed and for connectin said. souice of direct current to the collector rings of said rotor winding and said stator winding in series with said rotary transfori'ncr, whereby said dynamo electric machine operates as an alternating current liioostcr, for operation of said induction 1n0- 'tor at a i'liii'crent speed.

10. In a system oi m tor control, an induction motor, means for regulating the speed of said induction motor by utilizing nergy taken from the secondary of the induction motor comprising a. rotary transformer, a dynamo electric machine having a stator winding and a rotor winding pro vidcd with collector rings, a source of direct current. and means for eonnecting said dynamo electric machine in cascade between said rotary transformer and said induction motor for operation of said induction mo" tor at a low speed, and for connectin said source of direct current to the col actor rings of said rotor winding and said stator winding in series with said rotary transformer, whereby said dynamo electric machine operates as an alternating current booster, for operation of said induction m0- tor at a high speed.

11. In a system of motor control, an induction motor, means for regulating the speed of said induction motor by utilizing energy taken from the secondary of the induction motor comprising a rotary transfor'mer for transforming alternating current to direct current, a direct current machine mechanically connected to said induction motor and supplied with current from said rotary transformer, a dynamo electric machine ha ring a stator Winding and a r0- tor winding provided with collector rings, a Sourcrof direct current, and means for connecting said dynamo electric machine in cas ade between said rotary transformer and said induction motor {or operation of said induction motor at one speed and for connecting sai-l source of direct current to the collector rings of said rotor winding and said stator winding in series with said totary transformer, .rhcrehy said dynamo electric machine operates as an alternating current hooster, for operation of said induction motor at a different speed.

12. In a system of motor control, an induction motor, means for regulatin the speed of said induction motor by uti izing energy taken from the secondary of the induction motor comprising a rotary transformer for transforming alternating current to direct current, a direct current machine mechanically connected to said induction motor and supplied with current from said rotary transformer, a dynamo electric ma.- chine having astator winding and a rotor winding provided with collector rings, a source of direct current. and means for connecting said dynamo electric machine in cascade between said rotary transformer and said induction mote; for operation of said induction motor at a l speed and for connecting said source of direct current to the collector rings of said rotor Winding and said stator winding in series with said rotary transformer, whereby said dynamo electric machine operates as an alternating current booster, for operation of said induction mo tor at a high speed,

13. In asystem of motor control, an induction motor, means for regulating the speed of said induction motor by utilizing energy taken from the secondary of the in? duction motor comprising a rotary trans former, a dynamo electric machine mechanh,

supplied with current from said rotary transformer, a second dynamo electricianchine, and means for connecting said second dynamo electric machine in cascade between said rotary transformer and said in duetion motor for operation of said induction motor at one speed and for connecting said rotary transformer as a. simple rotary transformer for operation of said induction motor at a different speed.

cally connected to said induction motor and 14. In a system of motor control, an induction motor means for regulating the speed of said lnduction motor by utilizing energy taken from the secondary of the induction motor comprising a rotary transformer, a dynamo electric machine mechanically connected to said induction motor and supplied with current from said rotary transformer, a second dynamo electric machine, and means for connecting said second dynamo electric machine in cascade between said rotary transformer and said induction motor for o eration of said induction motor at low spee and for connecting said rotary transformer as a simple rotary transformer for operation ofsaid induction niotor at a high speed.

15. In a system of motor ,contrbl, an induction motor, means for regulatin the speed of said induction motor by at izing ener taken from the secondary of the inductlon motor comprising a rotary transformer, a dynamo electric machine. mechani-' cally connected to said induction motor and supplied with current from' said rotary transformer, a second dymhno electric machine, and means for c nnecting said second dynamo electric machi 0 either in cascade as a fre uency chahger or as an alternating current cost-er between said rotary trans former and said induction motor.

16. In a system ofmotor control, an induction motor, means for regulating the speed of said induction motor by utilizing energy taken from the secondary of the in duction motor comprising a rotary transformer, a dynamo electric machine mechanically connected to said induction motor and supplied with current from said rotary transformer, a second dynamo electric ma chine, and means for connecting said second dynamo electric machine in cascade as a frequency changer between said rotary transformer and said induction motor for operation of said induction motor at a slow speed and for connecting said second dynamo, electric machine as an alternating current booster in series with said rotary transformer for operation of said induction motor at a hi h speed.

17. n a system of motor control, an induction motor, means for regulating the speed of said induction motor by utilizing euer taken from the secondary of the induction motor comprising a rotary trans former, a dynamo electric machine mechanically connected to said induction motor and supplied with current from said rotary transformer, a second dynamo electric ma chine having a stator winding and a rotor winding provided with collector rings, a source of direct current, and means for core necting said second dynamo electric machine 1n cascade between said rotary trans former and said induction motor for opera-- tion of said motor at one speed and for con meeting said source of direct current to the collector rings of said rotor winding and said stator winding in series with said ro tary transformer, whereby said second dynamo electric machine operates as an alternating current booster, for operation of said, induction motor at a diflerent'speed.

18. In a system of motor control, an induction motor, means for regulating the speed of said induction motor by -utiiizing energy taken from the secondary of the iii-- duction motor comprising a rotary transformer, a dynamo electric machine mechani cally connected to said induction motor and supplied with current from said rotary transformer, a second dynamo electric machine having a stator winding and a rotor winding provided with collector rings, a source of direct current, and means for counesting said second dynamo electric machine 1 

